Quick test in template dev tool shows that the value stored in the iOS battery level is a string not an integer. So you can’t use it as a numeric_state.
you could use a template trigger and do the conversion like this: > {{states.sensor.sensor.robins_ipad_battery_level.state | int<10}}
You should also check the alert component as it may be more suited for battery level alert. (works basically the same way but keep notifiying every X minutes until you perform the action (either acknowlege in frontend or recharge the iPad).